• 한국환경보건학회지
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• 제19권3호
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• pp.29-35
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• 1993

This study was performed to obtain optimal conditions for reduction of color in dye wastewaters using coagulation-sedimentation processes with redox reactions. The reduction of color as well as organic matters variation was observed after coagulation-sedimentation processes using FeSO$_4$ $\cdot$ 7H$_2$O and NaOCl. Coagulation-redox reaction was done with the dose of Coagulant and oxidant at various pH values. Redox reaction was done through jar-mixing and aeration. The results of study were as follows: 1. In the coagulation-sedimentation processes using FeSO$_4$ $\cdot$ 7H$_2$O, color reduction was heigher at pH 3. With variance of dosage of FeSO$_4$ $\cdot$ 7H$_2$O, color reduction was higher at 250 mg/l. When coagulation-sedimentation using FeSO$_4$ $\cdot$ 7H$_2$O 250 mg/l was added at pH 3, the reduction of color, COD$_{Mn}$, and COD$_{Cr}$ showed 47.6%, 21.3% and 22.1%, respectively. 2. When NaOCI was added at level of 100 ppm in raw wastewater at pH 3, the reduction of color, COD$_{Mn}$, and COD$_{Cr}$ showed 30.2%, 5.5% and 6.2%, respectively. 3. After coagulation-sedimentation processes by addition of FeSO$_4$ $\cdot$ 7H$_2$O, when NaOCl was added at level of 250 mg/l in supernant, color reduction was 47.8% in aeration and 37.5% in jar-mixing. 4. Color reduction by aeration was higher than that by jar-mixing.

• Korean Journal of Chemical Engineering
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• 제35권11호
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• pp.2321-2326
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• 2018

We evaluated the optimal conditions for fluidization of nickel oxide (NiO) and its reduction into high-purity Ni during hydrogen reduction in a laboratory-scale fluidized bed reactor. A comparative study was performed through structural shape analysis using scanning electron microscopy (SEM); variance in pressure drop, minimum fluidization velocity, terminal velocity, reduction rate, and mass loss were assessed at temperatures ranging from 400 to $600^{\circ}C$ and at 20, 40, and 60 min in reaction time. We estimated the sample weight with most active fluidization to be 200 g based on the bed diameter of the fluidized bed reactor and height of the stocked material. The optimal conditions for NiO hydrogen reduction were found to be height of sample H to the internal fluidized bed reactor diameter D was H/D=1, reaction temperature of $550^{\circ}C$, reaction time of 60 min, superficial gas velocity of 0.011 m/s, and pressure drop of 77 Pa during fluidization. We determined the best operating conditions for the NiO hydrogen reduction process based on these findings.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2014년도 추계학술대회
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• pp.87-88
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• 2014

The Coastal sediment is highly contaminated due to ship transportation, industries discharges and urban sources. Various contaminants release into seawater and settle in marine sediment and it significantly affect marine eco system. In the present study evaluated the optimization of slow release biostimulant ball (BSB) in coastal sediment in busan. The effective variables like BSB size, distance and month variables on VS reduction was determined by using Response surface methodology(RSM). The analysis of variance (ANOVA) and coefficient determination (R2) of VS was 0.9369 and maximum reduction of VS was obtained in 3cm ball size and 5.5cm distance and 4 month interval time. This result revealed that the BSB in effective VS reduction in coastal sediment.

• 복식문화연구
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• 제14권6호
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• pp.900-916
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• 2006

The purposes of this study were to define housewife's risk perception and risk reduction behavior when purchasing children's wear, and to identify the differences according to the clothing buying behavior and demographic characteristics. Data were gathered through survey with 429 housewives in Seoul and metropolitan area, and then statistically analyzed by descriptive statistics, factor analysis, Analysis of Variance (ANOVA), Duncan's test, and Pearson's correlation analysis. The results showed partially significant differences in risk perception, especially economic risk and social psychological risks, among housewife consumer groups according to the clothing buying behavior and the demographic characteristics. There were significant differences in risk reduction behaviors among the groups, especially brand preference/industry information, observation/experience, and media information. Also, correlations between risk perception and risk reduction behaviors were found. The social psychological risk perception was highly correlated to the risk reduction behaviors, while the time/convenience loss risk was not correlated to any risk reduction behavior. The results of this study provide insight into children's wear business through suggesting marketing implication.

• 보건행정학회지
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• 제14권1호
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• pp.121-147
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• 2004

Since the pilot program for a DRG-based prospective payment system was introduced in 1997, the performance of KDRGs has been one of hotly debated issues. The objectives of this study are to refine the classification algorithm of the KDRGs and to assess the improvement achieved by the refinement. The U.S. Medicare DRGs version 17.0 and the Australian Refined DRGs version 4.1 were reviewed to identify areas of possible impro-vement. Refined changes in the classification and result of date analyses were submitted to a panel of 48 physicians for their reviews and suggestions. The refinement was evaluated by the variance reduction in resource utilization achieved by the KDRG The database of 2,182,168 claims submitted to the Health Insurance Review Agency during 2002 was used for evaluation. As the result of the refinement, three new MDCs were introduced and the number of ADEGs increased from 332 to 674. Various age splits and two to four levels of severity classification for secondary diagnoses were introduced as well. A total of 1,817 groups were defined in the refined KDRGs. The variance reduction for charges of all patients increased from 48.2％ to 53.6％ by the refinement, and from 65.6％ to 73.1％ for non-outlier patients. The r-square for length of stays of all patients was increased from 28.3％ to 32.6％, and from 40.4％ to 44.9％ for non-outlier patients. These results indicated a significant improvement in the classification accuracy of the KDRG system.

• 한국정보통신학회논문지
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• 제17권1호
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• pp.32-40
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• 2013

본 논문에서는 빔포밍과 입사각분석 기반 마스킹을 이용한 다채널 음성개선 알고리즘이 제안된다. 제안된 알고리즘에서는 LCMV 빔포밍을 수행한 후에 입사각 분석을 이용한 멜-주파수 위너필터가 적용되어 잔존하는 잡음을 제거한다. 성능 향상을 위해서 빔포밍의 적응 필터 학습률과 목표 음성 스펙트럼 검출을 위한 입사각 임계치가 최적화된다. 성능 지수로서 PESQ와 출력 SNR이 측정되었으며 실험 결과 제안한 알고리즘이 종전의 최소분산 빔포밍 기법보다 PESQ 관점에서 0.09, 출력 SNR 관점에서 5.75 dB의 성능 향상시킴을 알 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 하계학술대회 논문집 A
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• pp.666-670
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• 2004

This paper presents a new approach for determining an accurate incentive levels of Direct Load Control (DLC) program using sequential Monte Carlo Simulation (MCS) techniques. The economic analysis of DLC resources needs to identify the hourly-by-hourly expected energy-not-served resulting from the random outage characteristics of generators as well as to reflect the availability and duration of DLC resources, which results the computational explosion. Therefore, the conventional methods are based on the scenario approaches to reduce the computation time as well as to avoid the complexity of economic studies. In this paper, we have developed a new technique based on the sequential MCS to evaluate the required expected load control amount in each hour and to decide the incentive level satisfying the economic constraints. And also the proposed approach has been considered multi-state as well as two-state of the generating units. In addition, we have applied the variance reduction technique to enhance the efficiency of the simulation. To show the efficiency and effectiveness of the suggested method the numerical studies have been performed for the modified IEEE reliability test system.

• Nuclear Engineering and Technology
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• 제55권4호
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• pp.1428-1438
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• 2023

A novel Fission Diffusion Synthetic Acceleration (FDSA) method is developed and implemented as a part of a hybrid neutronics method for source convergence acceleration and variance reduction in Monte Carlo (MC) criticality calculations. The acceleration of the MC calculation stems from constructing a synthetic operator and solving a low-order problem using information obtained from previous MC calculations. By applying the P₁ approximation, two correction terms, one for the scalar flux and the other for the current, can be solved in the low-order problem and applied to the transport solution. A variety of one-dimensional (1-D) and two-dimensional (2-D) numerical tests are constructed to demonstrate the performance of FDSA in comparison with the standalone MC method and the coupled MC and Coarse Mesh Finite Difference (MC-CMFD) method on both intended purposes. The comparison results show that the acceleration by a factor of 3-10 can be expected for source convergence and the reduction in MC variance is comparable to CMFD in both slab and full core geometries, although the effectiveness of such hybrid methods is limited to systems with small dominance ratios.

• 한국산학기술학회논문지
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• 제16권12호
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• pp.8455-8461
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• 2015

본 논문에서는 라만 스펙트럼의 고속 탐색을 위해 특이값 분해(SVD, Singular Value Decomposition)를 이용한 새로운 탐색 알고리즘들을 제안한다. 제안 알고리즘에서는 SVD를 통해 얻은 특이벡터를 중요도에 따라 선별하여 실험에 사용함으로써 계산량 단축을 도모한다. 파일럿 테스트(Pilot test)를 수행하여 일부 데이터들을 미리 탐색 대상에서 제외시키고 부분탐색법(PDS, Partial Distance Search)을 적용하여 탐색을 수행함으로써 큰 폭으로 계산량을 감소시킨다. 실험에 사용한 데이터베이스는 총 14,032종의 화학 물질 라만 스펙트럼으로 구성하였으며, 기존의 탐색 방법인 전체탐색법(Full Search), PDS와 평균피라미드탐색법(MPS, Mean Pyramid Search)를 1차원공간상의 신호에 적용하기 적절하게 변형한 1DMPS에 PDS를 적용한 실험(1DMPS+PDS), 데이터의 분산을 내림차순 정렬하여 !DMPS와 PDS를 적용한 실험(1DMPS Sort with Variance+PDS), 데이터의 250차원 성분만 SVD 변환하여 PDS를 적용한 실험(250SVD+PDS), 그리고 제안 알고리즘 PSP(Partial SVD with PDS)와 PSSP(Partial SVD with Sorted Pilot test)을 적용한 실험을 비교 분석하였다. 각 알고리즘의 성능은 곱셈 및 덧셈의 연산량 비교를 통해 이루어졌는데, 실험 결과에 따르면 250SVD+PDS에 비해 제안알고리즘 PSP는 15.7%, PSSP에서는 64.8%의 계산량 감소를 확인하였다.

• Journal of Korean Neurosurgical Society
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• 제56권4호
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• pp.315-322
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• 2014

Objective : Posterior accessed lumbar interbody fusion (PALIF) has a clear objective to restore disc height and spinal alignment but surgeons may occasionally face the converse situation and lose lumbar lordosis. We analyzed retrospective data for factors contributing to a postoperative flat back. Methods : A total of 105 patients who underwent PALIF for spondylolisthesis and stenosis were enrolled. The patients were divided according to surgical type [posterior lumbar inter body fusion (PLIF) vs. unilateral transforaminal lumbar interbody fusion (TLIF)], number of levels (single vs. multiple), and diagnosis (spondylolisthesis vs. stenosis). We measured perioperative index level lordosis, lumbar lordosis, pelvic tilt, sacral slope, pelvic incidence, and disc height in standing lateral radiographs. The change and variance in each parameter and comparative group were analyzed with the paired and Student t-test (p<0.05), correlation coefficient, and regression analysis. Results : A significant perioperative reduction was observed in index-level lordosis following TLIF at the single level and in patients with spondylolisthesis (p=0.002, p=0.005). Pelvic tilt and sacral slope were significantly restored following PLIF multilevel surgery (p=0.009, p=0.003). Sacral slope variance was highly sensitive to perioperative variance of index level lordosis in high sacral sloped pelvis. Perioperative variance of index level lordosis was positively correlated with disc height variance ($R^2=0.286$, p=0.0005). Conclusion : Unilateral TLIF has the potential to cause postoperative flat back. PLIF is more reliable than unilateral TLIF to restore spinopelvic parameters following multilevel surgery and spondylolisthesis. A high sacral sloped pelvis is more vulnerable to PALIF in terms of a postoperative flat back.